In many receiver or transceiver applications, an amplifier is used to amplify a signal received prior to processing the amplified signal further, for instance, by downmixing the signal and further amplifying or otherwise processing the signal in an intermediate frequency or low frequency domain. In today's single stage received topologies, the amplifiers RF output signal (RF=radio frequency) is typically directly fed via a mixer to a trans-impedance-amplifier (TIA). In such a scenario, the amplifier's output impedance becomes one of many parameters, which may determine the over-all performance of such a topology.
However, also in other topologies, amplifiers are used to amplify received signals before further processing them, for instance, by downmixing, amplifying, filtering and so on. Also in these applications matching the impedances of the components, circuits or parts of circuits may become an important design goal.
Since a tendency exists to use more and more amplifier circuits in a single application to be compatible, for instance, with more than just one transmission technology, the available space becomes scarce for implementing amplifiers.
To counteract the number of amplifiers to be implemented, a tendency exists to implement amplifiers having wideband inputs, which may increase their configurability and have the potential to reduce the number of inputs. Naturally, also energy dissipation or energy consumption is especially in mobile applications an important key factor.